<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>header和footer</title>
    <link rel="stylesheet" href="index1.css">
    <style media="screen">

    </style>
  </head>
  <body>
    <header>页面标题
      <nav>导航</nav>
    </header>
    <aside>侧边栏</aside>
    <main>主内容</main>
    <footer>页尾</footer>
  </body>
</html>
